Turkey earthquake reveals a new active fault zone

TURKEY, one of the world’s most earthquake-prone countries, shook again last weekend. The magnitude 7.2 quake struck near the country’s eastern border and has so far claimed over 350 lives.

Most of the country lies on the small Anatolian plate, which is being squeezed westwards as the Arabian and Eurasian plates collide. Many of Turkey’s most severe quakes occur on one of the two faults that flank the Anatolian plate.

Between 1939 and 1999 Turkey’s major earthquakes seemed to be marching westwards along the north Anatolian fault towards Istanbul. In 1999 a magnitude-7.6 quake struck near Izmit, 70 kilometres from Istanbul, killing around 17,000 people.Since 2003, however, activity has shifted southwards to the east Anatolian fault.

According to the US Geological Survey, the latest quake’s epicentre was 16 kilometres north-east of Van in eastern Turkey, which places it near the junction of the two Anatolian faults. Here, tectonic activity is dominated by the Bitlis suture zone – a broad zone of compression between the Arabian and Eurasian plates.

“Since [the] quake is in the junction it’s hard to know which fault was responsible,” says Kevin McCue, director of the Australian Seismological Centre in Canberra. The USGS reports that the style of tectonic movement is consistent with compressional activity within the Bitlis suture zone rather than lateral grinding along the Anatolian faults.

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